Two-dimensional viewing surfaces such as televisions or movie screens are well known and have been used extensively to provide entertainment. Moving images are displayed on the television screens or movie screens which depict some pre-recorded or live activity. However, such images are two dimensional and consequently the entertainment effect is somewhat limited in that the viewer is constantly aware that what is being seen and heard is a severely limited version of similar events in the real (three dimensional) world.
Attempts have been made in the past to provide a three dimensional image. One such attempt is to polarize a pair of images and then superimpose them upon each other. A viewer then wears a pair of glasses which allows only the appropriate image to be received by the appropriate eye. An analogous procedure is the use of red and green blocking lenses in glasses. However, while producing a three dimensional image, such approaches do not afford 3 D sound, or, more importantly the impression that what is being viewed is real. This is because the image, though 3-dimensional is like looking through a small window (the t.v. screen) across the room. Further, the image can be somewhat blurred and the eye strain caused by looking through such glasses often creates discomforts such as headaches. Therefore, an alternative means of producing a moving three-dimensional image with matched three-dimensional sound is desired.
Another alternative is to provide a stereoscopic television headset, such as is disclosed in U.S. Pat. No. 2,955,156 entitled STEREOSCOPIC-TELEVISION APPARATUS FOR INDIVIDUAL USE, which was granted on Oct. 4, 1960. In this apparatus, a pair of television tube units are adjustably mounted within a casing behind a pair of optical units. The optical units include inner and outer peripheral vision lenses. The casing has a pair of eye openings and may be strapped around an individual's head. In this manner the individual is able to see an individual image in each eye. Through use of appropriate signal sources, a visual three-dimensional effect can be achieved.
However, this prior invention has a number of difficulties and disadvantages. Firstly, the use of cathode ray tubes so close to the eyes is unacceptable to most viewers because of the perceived risk of radiation from the tubes. Further, the casing 10 is relatively large and awkward, and cannot be comfortably placed on the person seeking the three-dimensional image; a strap around the back of the head is required. Further, the earphones 27 are large and awkward. Because of its size, weight and awkward attachment, the viewer is constantly aware the device is being worn, which reduces the persuasiveness of the three-dimensional visual experience. A further, fundamental, limitation of this prior invention is its lack of a suitable sound signal source to complement the visual image. The sound is merely left-sight stereo--without the forward-backward, up-and-down characteristics of sound as naturally perceived.